Determination of characteristics for mechanically separated organic fraction of MSW at a full-scale anaerobic digestion plant

Abstract

Anaerobic digestion (AD) as a waste management method has the potential to reduce greenhouse gas emissions while producing renewable energy, making it a viable option for managing the organic fraction of municipal solid waste (OFMSW). OFMSW characteristics can vary depending on factors such as waste source, composition and separation units. The characteristics of OFMSW are critical for analyzing and monitoring the AD process to optimize biogas production. In this study, the waste composition and physicochemical characteristics of the mechanically separated OFMSW (ms-OFMSW) were determined at a full-scale AD plant in Turkiye. The ms-OFMSW samples were collected monthly after mechanical separation and were subsequently sent to the anaerobic digester. The composition and physicochemical characteristics of the samples were determined by manual sorting. The results showed that the majority of the ms-OFMSW (76.45%+/- 1.71%) was organic, while 8.99%+/- 1.56% was recyclable and 14.56%+/- 1.69% was non-recyclable. Loss of environmental benefits for the recyclable materials was determined using a free online tool provided by Environmental Protection Agency. Metals (399.7 GJ) and plastics (403.7 GJ) both saved nearly the same amount of energy while metals saved the most water (421.8 m3), with the greatest positive impact. Greenhouse benefits ranged from 3 tons to 40 tons of carbon dioxide equivalent for each waste stream. These findings suggest that efficient pre-separation units can improve the anaerobic digestibility of OFMSW, while also providing greater environmental benefits by preventing recyclable waste from the anaerobic digester. In addition to encouraging source separation applications, this study demonstrates the need for improved technologies to separate OFMSW from mixed MSW.